Key seat guide sub



June 12, 1962 R. LEMONS 3,038,763

KEY SEAT GUIDE SUB Filed Jan. 5, 1961 INVTOR. ROY LEMOxNS ATTORNEYS States This invention relates generally to oil well tools and more particularly to a novel sub for insertion in a drill pipe string to guide the string away from key seats formed in the bore hole and thereby avoid sticking of the pipe in the hole.

During deflection drilling operations, the joints in the drill pipe string may be urged against the wall portion of the bore hole on the side of the deflection. The resulting rubbing action can wear a slot or cavity in the side wall, referred to as a key seat. The key seat generally has a diameter corresponding substantially to that of the outside diameter of the joints in the drill pipe string, or if flush joints are used, to that of the pipe string itself. As a consequence, in attempting to remove the drill pipe string, the drill collar, which is of larger diameter, may become wedged in the key seat.

To free a stuck drill pipe string in a key seat is a laborious and oftentimes expensive operation. Usually, a cutting operation on the key seat itself is necessary. Alternatively, the dril pipe itself may be severed to enable withdrawal.

With the foregoing in mind, it is a primary object of this invention to provide a novel sub for insertion in a drilling string which may be manipulated to guide the pipe in such a manner as to avoid catching of the drill collar on a key seat.

More particularly, it is an object to provide a novel tool for use in a drill pipe string which will enable guidance of a drill pipe collar past a key seat together with any other tools of larger diameter secured thereto without necessitating either severing the drill pipe or effecting cutting operations on the key seat itself.

Other objects of the invention are to provide an im proved tool for carrying out the foregoing objects which is extremely rugged, which does not employ any moving parts, and is adapted for simple insertion directly in a drilling string.

Briefly, these and other objects and advantages of this invention are attained by providing a sub comprising a tubular member having an enlarged diameter body between its upper and lower ends. The upper and lower ends themselves in turn are arranged to be connected between the drill collar and drill pipe string. The enlarged body is cut preferably on diametrically opposite sides in such a manner as to define sloping steps initiating at circumferentially spaced rear points of the body and terminating at lower forward spaced circumferential points on the body.

With the foregoing arrangement, there are effectively provided camming surfaces between which the body portion is of narrow dimension sufficient to be received in a key seat. By rotating the drill pipe to properly orient the sub such that this body portion between the sloping steps will be received within the key seat, subsequent upward movement will result in a camming of the sub and connected drill pipe collar away from the key seat, thus centering the drill pipe in the bore hole for easy removal.

A better understanding of the invention will be had by now referring to a preferred embodiment thereof as illustrated in the accompany drawings, in which:

FIGURE 1 is a perspective view of the key seat guide sub of this invention;

FIGURE 2 is a front perspective view; and,

FIGURE 3 is a top cross-sectional view of the sub within a bore hole having a key seat.

atent Referring to FIGURES 1 and 2, the sub comprises a tubular member 10 having upper and lower threaded ends 11 and 12 for insertion between the lower end of a conventional drill pipe and the drill collar of the drill bit, respectively. As shown, between the upper and lower ends 11 and 12, there is provided an enlarged diameter body 13. This body is cutaway on diametrically opposite sides as indicated at 14 and 15 in such a manner as to define sloping steps 16 and 17. As shown, these steps initiate at spaced upper rear circumferential points 18 and 19 on the body 13 and terminate at spaced lower front circumferential points 20 and 21 on the lower portion of the body 13.

Preferably, the distance d between these circumferential points, as shown best in FIGURE 2, is substantially equal to the outside diameter of the joints in the drill pipe string to which the tubular member 10 is connected. This diameter corresponds substantially to the outside diameter of the upper and lower end portions of the tubular member 10 as shown in both FIGURES 1 and 2.

Referring now to FIGURE 3, the manner in which the key seat guide sub of this invention operates will be understood. Initially, the sub is inserted between the end of a string of drill pipe and a drill collar by simply threading the upper end 11 to the end of the pipe string and then threading the drill bit collar onto the lower end 12.

In FIGURE 3, there is shown a bore hole 22 along one side of which there has been a formed a key seat 23 as a consequence of deflection drilling in a direction to the right as viewed in FIGURE 3. To prevent wedging or catching of the drill pipe collar, which is of larger diameter than the key seat, upon removal of the drill pipe string from the bore hole 22, the key seat guide sub 10 is used. Thus, the pipe string is rotated to rotate the sub until the portion of the enlarged diameter body 13 between the sloping steps 16 and 17 can be received Within the key seat 23.

With the sub positioned as illustrated in FIGURE 3, it will be evident that the sloping steps 16 and 17 will engage the corners 24 and 25 of the key seat 23 such that upward pulling on the drill pipe string will result in a camming to the left of the sub and attached drill pipe string and drill collar as indicated by the arrow. This camming action will thus guide the drill collar away from the key seat and center the drill pipe string, thereby facilitating removal from the bore hole.

While only one particular embodiment of this invention has been set forth, it should be understood by those skilled in the art that various modifications and changes can be made without departing from the spirit and scope of the invention. The key seat guide sub is therefore not to be thought of as limited to the exact structure set forth and described.

What is claimed is:

1. A key seat guide subcomprising: an integral tubular member having an enlarged diameter body intermediate its ends with opposite sides cut away to define sloping steps initiating at upper rear circumferential points on said body and terminating at lower forward circumferential points on said body.

2. A key seat guide sub, according to claim 1, in which said tubular member includes connecting means at its upper and lower ends for securement in a drill pipe string.

3. A key seat guide sub comprising: a tubular member having its upper and lower ends threaded for insertion between the end of a drill pipe string and drill collar, said member including an enlarged body between its upper and lower ends of diameter greater than the outside diameter of the joints in said drill pipe string,

a ossges 1.) said body having opposite sides cut away to define sloping steps initiating at upper rear circumferential points on said body and terminating at lower forward circumferential points on said body, said upper circumferential points being spaced apart the same distance as said lower circumferential points.

4. A key seat guide sub acording to claim 3, in which said distance is substantially equal to the outside diameter of said joints in said drill pipe string whereby a 4 key seat formed by said joints can receive the portion of said body between said sloping steps, upward movement of said sub thence camrning said sub and connected drill pipe collar away from said key seat.

References Qited in the file of this patent UNITED STATES PATENTS 2,014,805 Hinderliter Sept. 17, 1935 

